Interplay Between Deep Convection and Mesoscale Gravity Waves

Abstract

Although the association between precipitation and mesoscale gravity waves (MGWs) is well documented, the feedback mechanisms governing their amplification remain difficult to isolate. This study uses convection‐permitting numerical simulations with 1–4 km grid spacing to investigate a complex MGW event that occurred over the south‐central United States on 7 March 2008. The waves developed within a recurring synoptic environment characterized by a pronounced pre‐existing baroclinic zone and highly curved jet streak circulation. However, following the onset of deep convection, the wave modes diverged markedly in structure and energetics, demonstrating strong sensitivity to precipitation system. The event transitioned from a moderate‐amplitude, dry MGW of depression to a high‐amplitude, moist‐wave regime comprising an MGW of elevation and a MGW of depression . It was embedded with a localized mesohigh–wake‐low pressure couplet. Two‐dimensional ray‐tracing and four‐dimensional Lagrangian back‐trajectory analyses demonstrate that differences between the dry and moist wave packets were partly attributable to the direct influence of moist convection on the generation and maintenance of the secondary wave mode and the rapid amplification of the primary wave mode. Comparison of CTRL with a “fake‐dry” experiment, where moist diabatic processes were suppressed, shows that convective thermodynamic forcing and midtropospheric jetlet circulations trigger a secondary wave mode. Nonlinear balance residual and Lagrangian Rossby number diagnostics indicate that was modulated by upper‐level jet‐imbalance forcing near southeastern Texas before propagating northeastward into Louisiana without further amplification. These results show how multiscale diabatic and dynamical interactions generate localized pressure perturbations and sustain a high‐impact MGW event.